Auburn researchers identify natural enemy of kudzu bug

Auburn University researchers have discovered a natural enemy of the kudzu bug, an insect pest that damages soybeans in Alabama.

By Paul Hollis

Auburn University entomologists have discovered and identified a tiny wasp that could provide a huge benefit to Alabama soybean producers and other farmers.

Though only about the size of a pinhead, the newly detected parasitoid wasp, Ooencyrtus nezarae, can do plenty of damage to the kudzu bug, a quarter-inch-long invasive pest of soybeans and other legume crops in the Southeast. Researchers in the lab of entomologist Henry Fadamiro, associate dean for research for the College of Agriculture and associate director of the Alabama Agricultural Experiment Station, were the first to detect the wasp’s presence in North America.

The research team published its findings in a recent article in the Journal of Insect Science. Blessing Ademokoya, an Auburn graduate researcher at the time of the study and now a Ph.D. student at the University of Nebraska–Lincoln, is lead author of the article. Fadamiro and Rammohan Balusu, research fellow in the Department of Entomology and Plant Pathology, are co-authors, as are Auburn research entomologist Charles Ray and Jason Mottern, entomologist at the USDA Smithsonian Institution in Washington, D.C. Ray and Mottern assisted in final identification of the wasp.

Ooencyrtus nezarae is the second kudzu bug–attacking wasp to be identified in the U.S. The first, Paratelenomus saccharalis, was discovered in Georgia in 2013.

“It is exciting to know that many natural enemies are in the field helping to keep kudzu bug populations under control,” Ademokoya said. “And, with this latest addition, we have a potential explanation for the decline observed in kudzu bug densities across several locations in the southeastern U.S.”

The kudzu bug, native to Asia, was first reported in the U.S. in 2009 in Georgia. Although it feeds on kudzu—an economically important invasive weed native to Asia and familiar to Southerners—it also devours soybeans and other legume crops, causing significant yield loss in highly infested fields.

A strong flyer and good hitchhiker, the pest rapidly expanded its numbers across many southern states, including Alabama, South Carolina, North Carolina, Florida, Tennessee, Mississippi, Virginia, Kentucky, Louisiana, Arizona, Maryland and Delaware. The population peaked in 2013.

The kudzu bug has emerged as the top yield-limiting pest of soybeans, which rank as the second most planted field crop in the United States with an estimated annual market value of approximately $39 billion.

In 2017, Alabama farmers harvested approximately 345,000 acres of soybeans with a production value of more than $150 million.

Potential long-term solution

Ooencyrtus nezarae, which was found during field surveys in Alabama, is reported to parasitize eggs from a variety of plant bug families in China.

“Until now, the distribution of O. nezarae has been limited to China, Japan, Thailand, South Korea and Brazil,” Fadamiro said. “This is the first report of the parasitoid in North America. The high rate of parasitism—82.8 to 100 percent—recorded in our study indicates that the parasitoid may serve as a potential long-term solution for managing kudzu bug.”

Despite O. nezarae’s high parasitism rate of kudzu bug, it has a short period of activity, and Fadamiro said continued research will be necessary to identify tactics for the use of the insect to biologically control the pest on farms.

“We need to conduct monitoring to know the distribution of the parasitoid in the United States and to determine its seasonal phenology in the field—when it is not active and when it is most active,” he said. “We also are interested in studying the nutritional ecology of this insect and strategies for its conservation in the field. We don’t want to spray toxic chemicals when it is most active.”

There are numerous ways to use natural enemies in production agriculture, Fadamiro said, including introducing them into areas where they are not already present and preserving them where they are naturally occurring. Farmers also can plant host flowering plants around a field so the nectar will attract and keep the beneficial insect in an area.

“If we conduct a survey and find the insects are only in central Alabama, then we can capture and relocate them to other areas of the state where the kudzu bug is a threat,” he said. “We want to make sure this finding is useful to the farmers who need it most.”

But there’s a risk in assuming that the known natural enemies of the kudzu bug will eliminate the threat, Fadamiro said.

“While the incidence of the kudzu bug has declined in recent years, there could be many factors involved, including weather conditions and other natural enemies, so we need to continue this work,” he said.

The research leading to the discovery of the parasitoid was supported by an Agriculture and Food Research Initiative Competitive Grant from the USDA National Institute of Food and Agriculture and by the Alabama Agricultural Experiment Station.